In one popular design of a cathode-ray tube for use in a television display, a getter container is carried or supported on a leaf spring that is attached to and extends from the electron-gun mount assembly. This combination is sometimes referred to as an antenna getter assembly. With the getter container supported in this fashion from the mount assembly, the getter container can be located in an area of the tube where it is more effective for flashing the getter material and, at the same time, can be removed and replaced with the mount assembly should the tube be regunned.
The spring itself usually consists of a spring steel ribbon that is shaped as an arc of a circle. One end of the ribbon is welded to the mount assembly and the other end is welded to the getter container. When the mount assembly and getter assembly are installed in the tube through the neck thereof, the spring extends toward the tube target and away from the longitudinal axis of the tube. Because of its arcuate shape and spring characteristic, the spring urges the getter container against the inner funnel wall of the tube. A typical shadow-mask-type tube of this design is described in U.S. Pat. No. 3,508,105 to N. P. Pappadis.
The getter container is usually provided with runners so that when the container is pushed into the tube during installation, it will slide over the inner surface of the tube envelope and over the inner coatings thereon. Unfortunately, the runners chip or/and scrape off particles of coating material and, in some cases, particles of envelope material. Particles of any type are detrimental to the tube performance. Conducting particles can cause arcing and stray emissions especially in the mount assembly. Insulating particles can collect electrostatic charges and cause localized distortions in the internal electric fields and in the electron beam path. Insulating particles are particularly undesirable when they settle on the shadow mask of the tube.
In order to avoid contacting the getter container and/or the runners with the inner surfaces of the envelope during installation, U.S. Pat. Nos. 3,711,734 to E. Yamazaki et al and 3,848,154 to R. J. Bowes et al each propose employing a bimetal spring. In both proposals, the spring is essentially straight when the getter container is pushed into the tube envelope and subsequently becomes arcuate. In the former patent, the bimetal spring is hot when installed and becomes arcuate upon cooling. In the latter patent, the spring is cool when installed and, when heated above some threshold temperature, one metal experiences a permanent dimensional change, which persists upon cooling, and the spring becomes arcuate.